PURPOSE: To provide such a heavy part replacing device that allows a heavy part to be replaced even by one person sccurately and safely.

CONSTITUTION: A vertical support post 9 is installed upright on the upper board 7 of a jack mechanism 6 which is made freely movable up and down, and a horizontal arm 10 which has a loop portion 11 on its end is installed rotatably on the top end portion of the support post 9. One of hoopks 14a and 14b on both ends of a rope member 14 is selected for supporting a heavy part and guided into the loop portion 11 at the end of the horizontal arm 10, and the other end of the rope member 14 is freely fixed to the upper board 7 or the support post 9.